Conjugated polymers containing special fluorene structural elements with improved properties

ABSTRACT

The invention relates to novel polymers containing fluorene structural elements, monomer parent compounds upon which said polymers are based, and the use of said inventive polymers as organic semiconductors and/or as electroluminescent material, in addition to electroluminescent devices containing said polymers.

There is considerable industrial demand for large-area solid-state lightsources for a number of applications, predominantly in the area ofdisplay elements, display-screen technology and illumination technology.The requirements made of these light sources cannot at present becompletely satisfied by any of the existing technologies.

As an alternative to conventional display and illumination elements,such as incandescent lamps, gas-discharge lamps andnon-self-illuminating liquid-crystal display elements,electroluminescent (EL) materials and devices, such as light-emittingdiodes (LEDs), have already been in use for some time.

Besides inorganic electroluminescent materials and devices,low-molecular-weight, organic electroluminescent materials and deviceshave also been known for about 30 years (see, for example, U.S. Pat. No.3,172,862). Until recently, however, such devices were greatly limitedin their practical applicability.

WO 90/13148 and EP-A-0 443 861 describe electroluminescent devices whichcontain a film of a conjugated polymer as light-emitting layer(semiconductor layer). Such devices offer numerous advantages, such asthe possibility of manufacturing large-area, flexible displays simplyand inexpensively. In contrast to liquid-crystal displays,electroluminescent displays are self-illuminating and therefore do notrequire an additional illumination source at the back.

A typical device in accordance with WO 90/13148 consists of alight-emitting layer in the form of a thin, dense polymer film(semiconductor layer) containing at least one conjugated polymer. Afirst contact layer is in contact with a first surface, and a secondcontact layer is in contact with a further surface of the semiconductorlayer. The polymer film of the semiconductor layer has a sufficientlylow concentration of extrinsic charge carriers so that, on applicationof an electric field between the two contact layers, charge carriers areintroduced into the semiconductor layer, the first contact layerbecoming positive compared with the other layer, and the semiconductorlayer emits radiation. The polymers used in such devices are conjugated.The term “conjugated polymer” is taken to mean a polymer which has adelocalized electron system along the main chain. The delocalizedelectron system gives the polymer semiconductor properties and enablesit to transport positive and/or negative charge carriers with highmobility.

For use in EL elements as described in WO 90/13148, very many differentpolymers have already been proposed. Derivatives ofpoly(p-phenylenevinylene) (PPV) appear particularly suitable. Suchpolymers are described, for example, in WO 98/27136. These polymers areparticularly suitable for electroluminescence in the green to redspectral region. In the blue to blue-green spectral region, the polymersproposed hitherto are principally those based on poly-p-phenylene (PPP)or polyfluorene (PF). Corresponding polymers are described, for example,in EP-A-0 707 020, WO 97/05184 and WO 97/33323. These polymers alreadyexhibit good EL properties, although development is still not completeby far. Thus, polymers in the blue to blue-green spectral regionfrequently also exhibit the phenomenon of morphological instability. Forexample, many polyfluorenes exhibit liquid-crystalline or relatedbehavior, which can result, in thin films, in domain formation, which isin turn unsuitable for the production of a homogeneously luminous area.These polymers also tend to form aggregates, which shifts theelectroluminescence into the long-wave region in an undesired manner,and adversely affects the life of the EL elements.

The object of the present invention was therefore to provide polymerswhich are suitable for emission in the blue and blue-green spectralregion and at the same time have improved morphological behavior.

Surprisingly, it is now been found that selection of specificsubstitution patterns in otherwise typical polymers principally built upfrom 2,7-fluorenyl units significantly improves the morphologicalproperties without losing the very good applicational properties(emission color, quantum yield of the emission, suitability for ELapplications).

The polymers according to the invention contain fluorene units whosesubstitution pattern makes them suitable for suppressing aggregation inthe film. This is achieved in particular by the 9,9-position beingsubstituted by two different types of aromatic radical. This result issurprising, principally in view of indications in the scientificliterature (G. Klärner et al., Adv. Mater. 1998, 10, 993), according towhich incorporation of diphenylfluorene units in the main chain does notgive such effects. However, this also means precisely that it has provenparticularly favorable to introduce two different aromatic substituentsin this position.

The invention relates to conjugated polymers which contain structuralunits of the formula (I)

in which

R¹ and R² are two different substituents from the group consisting ofC₂-C₄₀-heteroaryl and C₅-C₄₀-aryl, where the abovementioned aryl and/orheteroaryl radicals can be substituted by one or more substituents R³;for the purposes of this invention, the aryl and/or heteroaryl radicalsmust be of different types even if they differ through the nature orposition of substituents,

R³ and R⁴ are identical or different and are C₁-C₂₂-alkyl,C₂-C₂₀-heteroaryl, C₅-C₂₀-aryl, F, Cl, CN, SO₃R⁵ or NR⁵R⁶, where thealkyl radicals can be branched or unbranched or alternatively can becycloalkyl radicals, and individual, non-adjacent CH₂ groups of thealkyl radical can be replaced by O, S, C═O, COO, N—R⁵ or simple arylradicals, where the abovementioned aryl radicals can be substituted byone or more non-aromatic substituents R³,

R⁵ and R⁶ are identical or different and are H, C₁-C₂₂-alkyl,C₂-C₂₀-heteroaryl or C₅-C₂₀-aryl, where the alkyl radicals can bebranched or unbranched or alternatively can be cycloalkyl radicals, andindividual, non-adjacent CH₂ groups of the alkyl radical can be replacedby O, S, C═O, COO, N—R⁵ or simple aryl radicals, where theabovementioned aryl radicals can be substituted by one or morenon-aromatic substituents R³, and

m and n are each an integer 0, 1, 2 or 3, preferably 0 or 1.

R¹ and R² are preferably two different substituents from the groupconsisting of C₅-C₄₀-aryl and C₂-C₄₀-heteroaryl, where theabove-mentioned aryl and heteroaryl radicals can be substituted by oneor more substituents R³.

The polymer according to invention contains at least 10 mol %,preferably from 10 mol % to 100 mol %, of structural units of theformula (I) incorporated randomly, alternately, periodically or inblocks.

The polymers according to the invention are preferably copolymersconsisting of one or more structural units of the formula (I). In afurther embodiment of the present invention, the polymer according tothe invention may also contain different structural units of the formula(I) and further structural units which are not per se according to theinvention. Examples of such further monomers are 1,4-phenylenes,4,4′-biphenyls and further 2,7-fluorenes, which, if desired, can alsocarry substituents, preferably branched or unbranched C₁-C₂₂-alkyl or-alkoxy groups.

The polymers according to the invention generally have from 10 to 10000,preferably from 10 to 5000, particularly preferably from 50 to 5000,very particularly preferably from 50 to 1000, recurring units.

Particular preference is given to polymers in which m and n are zero.

The polymers according to invention can be built up by a wide variety ofreactions. However, preference is given to uniform C—C couplingreactions, for example the Suzuki condensation and the Stillecondensation. In this context, the term “uniform C—C coupling reaction”is taken to mean that the linking to the polymer is determined by theposition of the reactive groups in the corresponding monomers. This isgiven particularly well by the abovementioned reactions, which are veryhighly suitable owing to the clean course. Also suitable isnickel-catalyzed coupling of halogenated aromatic compounds (Yamamotocoupling). Less suitable, by contrast, are oxidative processes (forexample oxidative coupling using Fe(III) salts) since these result inundefined links.

The above comments also result in the preferred choice of monomers:these represent corresponding bishalogen, bispseudohalogen (i.e. in thesense of this invention e.g. bistriflate, bisnonaflate or bistosylate),bisboronic acid, bisstannate, monohalomonoboronic acid andmonohalomonostannate derivatives of the compounds of the formula (I) andformula (II).

The synthesis of the polymers according to the invention is shown inillustrative terms by Scheme 1 below:

The radical R in the above scheme is hydrogen or any desired organicradical, preferably a radical having 1 to 40 carbon atoms. Examplesthereof are corresponding alkyl radicals, for example methyl or butyl.Furthermore, R can be an aromatic radical having 5 to 30 carbon atoms,which can, if desired, be substituted. The radical R^(1a) corresponds inits definition to the radical R¹; the radical R^(2a) corresponds in itsdefinition to the radical R²; the radical R^(3a) corresponds in itsdefinition to the radical R³; the radical R^(4a) corresponds in itsdefinition to the radical R⁴.

Scheme 1 shows polymerization by Suzuki coupling. It is expresslypointed out that this is merely one possible embodiment. Othercombinations of boronic acids and halogens/pseudohalogens are of coursealso feasible. The Stille polymerization can also be carried outanalogously using corresponding tin compounds.

The Suzuki polymerization should be carried out as follows:

The monomers on which the structural unit of the formula (I) is based(and, if desired, further additional monomers containing correspondingactive leaving groups) are reacted in an inert solvent at a temperaturein the range from 0° C. to 200° C. in the presence of a palladiumcatalyst. It must be ensured here that the totality of all monomers usedhas a highly balanced ratio of boronic acid functions to halogen orpseudohalogen functions. In addition, it may prove advantageous toremove any excess reactive groups at the end of the reaction byend-capping with monofunctional reagents.

In order to carry out the above reaction with boronic acids (esters),the aromatic boron compounds, the aromatic halogen compounds, a base andcatalytic amounts of the palladium catalyst are introduced into water orinto one or more inert organic solvents or preferably into a mixture ofwater and one or more inert organic solvents, and stirred at atemperature of from 0 to 200° C., preferably from 30 to 170° C.,particularly preferably from 50 to 150° C., especially preferably from60° C. to 120° C., for a period of from 1 hour to 200 hours, preferablyfrom 5 hours to 150 hours, particularly preferably from 24 hours to 120hours. It may also prove advantageous here to meter in one type ofmonomer (for example a bisboronic acid derivative) continuously orbatchwise slowly over an extended period in order thus to regulate themolecular weight. The crude product can be purified by methods known tothe person skilled in the art and appropriate for the respectivepolymer, for example repeated re-precipitation or even by dialysis.

Suitable organic solvents for the process described are, for example,ethers, for example diethyl ether, dimethoxyethane, diethylene glycoldimethyl ether, tetrahydrofuran, dioxane, dioxolane, diisopropyl etherand tert-butyl methyl ether, hydrocarbons, for example hexane,isohexane, heptane, cyclohexane, toluene and xylene, alcohols, forexample methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol,1-butanol, 2-butanol and tert-butanol, ketones, for example acetone,ethyl methyl ketone and isobutyl methyl ketone, amides, for exampledimethylformamide, dimethylacetamide and N-methylpyrrolidone, nitriles,for example acetonitrile, propionitrile and butyronitrile, and mixturesthereof.

Preferred organic solvents are ethers, such as dimethoxyethane,diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, diisopropylether and t-butyl methyl ether, hydrocarbons, such as hexane, heptane,cyclohexane, toluene and xylene, alcohols, such as methanol, ethanol,1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol and ethyleneglycol, ketones, such as ethyl methyl ketone and isobutyl methyl ketone,amides, such as dimethylformamide, dimethylacetamide andN-methylpyrrolidone, and mixtures thereof.

Particularly preferred solvents are ethers, for example dimethoxyethaneand tetrahydrofuran, hydrocarbons, for example cyclohexane, toluene andxylene, alcohols, for example ethanol, 1-propanol, 2-propanol, 1-butanoland tert-butanol, and mixtures thereof.

In a particularly preferred variant, water and one or more solvents areemployed in the process described. Examples are mixtures of water andtoluene, water, toluene and tetrahydrofuran, and water, toluene andethanol.

Bases which are preferably used in the process described are alkalimetal and alkaline earth metal hydroxides, alkali metal and alkalineearth metal carbonates, alkali metal hydrogencarbonates, alkali metaland alkaline earth metal acetates, alkali metal and alkaline earth metalalkoxides and primary, secondary and tertiary amines.

Particular preference is given to alkali metal and alkaline earth metalhydroxides, alkali metal and alkaline earth metal carbonates and alkalimetal hydrogencarbonates.

Special preference is given to alkali metal hydroxides, such as sodiumhydroxide and potassium hydroxide, and alkali metal carbonates andalkali metal hydrogencarbonates, such as lithium carbonate, sodiumcarbonate and potassium carbonate.

The base is preferably employed in the process described in a proportionof from 100 to 1000 mol %, particularly preferably from 100 to 500 mol%, very very particularly preferably from 150 to 400 mol %, especiallyfrom 180 to 250 mol %, based on boron groups.

The palladium catalyst contains palladium metal or a palladium(0) or(II) compound and a complex ligand, preferably a phosphine ligand. Thetwo components can form a compound, for example the particularlypreferred Pd(PPh3)4, or be employed separately.

Examples of suitable palladium components are palladium compounds, suchas palladium ketonates, palladium acetylacetonates, nitrilopalladiumhalides, olefinpalladium halides, palladium halides, allylpalladiumhalides and palladium biscarboxylates, preferably palladium ketonates,palladium acetylacetonates, bis-η²-olefinpalladium dihalides,palladium(II) halides, η³-allylpalladium halide dimers and palladiumbiscarboxylates, very particularly preferablybis(dibenzylideneacetone)palladium(0) [Pd(dba)₂)], Pd(dba)₂ CHCl₃,palladium bisacetylacetonate, bis(benzonitrile)palladium dichloride,PdCl₂, Na₂PdCl₄, dichlorobis(dimethyl sulfoxide)palladium(II),bis(acetonitrile)palladium dichloride, palladium(II) acetate,palladium(II) propionate, palladium(II) butanoate and(1c,5c-cyclooctadienyl)palladium dichloride.

The catalyst used can likewise be palladium in metallic form, referredto below simply as palladium, preferably palladium in powdered form oron a support material, for example palladium on activated carbon,palladium on aluminum oxide, palladium on barium carbonate, palladium onbarium sulfate, palladium on aluminum silicates, such asmontmorillonite, palladium on SiO₂ and palladium on calcium carbonate,in each case having a palladium content of from 0.5 to 10% by weight.Particular preference is given to palladium in colloidal or powderedform, palladium on activated carbon, palladium on barium carbonateand/or calcium carbonate and palladium on barium sulfate, in each casehaving a palladium content of from 0.5 to 10% by weight. Specialpreference is given to palladium on activated carbon having a palladiumcontent of 5 or 10% by weight.

The palladium catalyst is employed in the process according to inventionin a proportion of from 0.01 to 10 mol %, preferably from 0.05 to 5 mol%, particularly preferably from 0.1 to 3 mol %, especially preferablyfrom 0.1 to 1.5 mol %, based on the halogen groups.

Examples of ligands which are suitable for the process are phosphines,such as trialkylphosphines, tricycloalkylphosphines andtriarylphosphines, where the three substituents on the phosphorus may beidentical or different and chiral or achiral and where one or more ofthe ligands can link the phosphorus groups of a plurality of phosphinesand where part of this link can also be one or more metal atoms.

Examples of phosphines which can be used in the process described hereare trimethylphosphine, tributylphosphine, tricyclohexylphosphine,triphenylphosphine, tritolylphosphine,tris-(4-dimethylaminophenyl)phosphine, bis(diphenylphosphino)methane,1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane and1,1′-bis(diphenylphosphino)ferrocene.

Other suitable ligands are, for example, diketones, for exampleacetylacetone and octafluoroacetylacetone, and tert-amines, for exampletrimethylamine, triethylamine, tri-n-propylamine and triisopropylamine.

Preferred ligands are phosphines and diketones, particularly preferablyphosphines.

Very particularly preferred ligands are triphenylphosphine,1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane and1,1′-bis(diphenylphosphino)ferrocene, in particular triphenylphosphine.

Also suitable for the process are water-soluble ligands which contain,for example, sulfonic acid salt and/or sulfonic acid radicals and/orcarboxylic acid salt and/or carboxylic acid radicals and/or phosphonicacid salt and/or phosphonic acid radicals and/or phosphonium groupsand/or peralkylammonium groups and/or hydroxyl groups and/or polyethergroups having a suitable chain length.

Preferred classes of water-soluble ligands are phosphines substituted bythe above groups, such as trialkylphosphines, tricycloalkylphosphines,triarylphosphines, dialkylarylphosphines, alkyldiarylphospines andheteroarylphosphines, such as tripyridylphosphine and trifurylphosphine,where the three substituents on the phosphorus may be identical ordifferent and chiral or achiral and where one or more of the ligands canlink the phosphorus groups of a plurality of phosphines and where partof this link can also be one or more metal atoms, phosphites,phosphinates and phosphonates, phosphols, dibenzophosphols, and cyclicand oligo- and polycyclic compounds containing phosphorus atoms.

The ligand is employed in the process in a proportion of from 0.1 to 20mol %, preferably from 0.2 to 15 mol %, particularly preferably from 0.5to 10 mol %, especially preferably from 1 to 6 mol %, based on thearomatic halogen groups. It is also possible, if desired, to employmixtures of two or more different ligands.

Advantageous embodiments of the Suzuki variant of the process aredescribed for low-molecular-weight couplings in, for example, WO94/10105, EP-A-679 619, WO-A-694 530 and PCT/EP 96/03154, which areexpressly incorporated herein by way of reference.

The Stille polymerization should be carried out as follows:

The monomers on which the structural units of the formulae (I) and (II)are based (and, if necessary, further monomers containing correspondingactive leaving groups) are reacted in an inert solvent at a temperaturein range from 0° C. to 200° C. in the presence of a palladium-containingcatalyst. It must be ensured here that the totality of all monomers usedhas a highly balanced ratio of organotin functions to halogen orpseudohalogen functions. In addition, it may prove advantageous toremove any excess reactive groups at the end of the reaction byend-capping with monofunctional reagents.

A review of this reaction is given, for example, in J. K. Stille, Angew.Chemie Int. Ed. Engl. 1986, 25, 508.

In order to carry out the process, aromatic tin compounds and aromatichalogen compounds are preferably introduced into one or more inertorganic solvents and stirred at a temperature of from 0 to 200° C.,preferably from 30 to 170° C., particularly preferably from 50 to 150°C., especially preferably from 60° C. to 120° C., for a period of from 1hour to 200 hours, preferably from 5 hours to 150 hours, particularlypreferably from 24 hours to 120 hours. It may also prove advantageoushere to meter in one type of monomer (for example a bisstannylderivative) continuously or batchwise slowly over an extended period inorder thus to regulate the molecular weight. The crude product can bepurified by methods known to the person skilled in the art andappropriate for the respective polymer, for example repeatedre-precipitation or even by dialysis.

Suitable organic solvents for the process described are, for example,ethers, for example diethyl ether, dimethoxyethane, diethylene glycoldimethyl ether, tetrahydrofuran, dioxane, dioxolane, diisopropyl etherand tert-butyl methyl ether, hydrocarbons, for example hexane,isohexane, heptane, cyclohexane, benzene, toluene and xylene, alcohols,for example methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol,1-butanol, 2-butanol and tert-butanol, ketones, for example acetone,ethyl methyl ketone and isobutyl methyl ketone, amides, for exampledimethylformamide (DMF), dimethylacetamide and N-methylpyrrolidone,nitriles, for example acetonitrile, propionitrile and butyronitrile, andmixtures thereof.

Preferred organic solvents are ethers, such as dimethoxyethane,diethylene glycol dimethyl ether, tetrahydrofuran, dioxane anddiisopropyl ether, hydrocarbons, such as hexane, heptane, cyclohexane,benzene, toluene and xylene, alcohols, such as methanol, ethanol,1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol and ethyleneglycol, ketones, such as ethyl methyl ketone, and amides, such as DMF.

Particularly preferred solvents are amides, very particularly preferablyDMF.

The palladium and phosphine components should be selected analogously tothe description for the Suzuki variant.

The present invention furthermore relates to the monomeric precursors onwhich the polymers according to the invention are based. These are givenby the formula (A)

in which

R¹ and R² are two different substituents from the group consisting ofC₂-C₄₀-heteroaryl and C₅-C₄₀-aryl, where the abovementioned aryl andheteroaryl radicals can be substituted by one or more substituents R³;for the purposes of this invention, the aryl and heteroaryl radicalsmust be of different types even if they differ through the nature orposition of substituents,

R³ and R⁴ are identical or different and are C₁-C₂₂-alkyl,C₂-C₂₀-heteroaryl, C₅-C₂₀-aryl, F, Cl, CN, SO₃R⁵ or NR⁵R⁶, where thealkyl radicals can be branched or unbranched or alternatively can becycloalkyl radicals, and individual, non-adjacent CH₂ groups of thealkyl radical can be replaced by O, S, C═O, COO, N—R⁵ or simple arylradicals, where the abovementioned aryl radicals can be substituted byone or more non-aromatic substituents R³,

R⁵ and R⁶ are identical or different and are H, C₁-C₂₂-alkyl,C₂-C₂₀-heteroaryl or C₅-C₂₀-aryl, where the alkyl radicals can bebranched or unbranched or alternatively can be cycloalkyl radicals, andindividual, non-adjacent CH₂ groups of the alkyl radical can be replacedby O, S, C═O, COO, N—R⁵ or simple aryl radicals, where theabovementioned aryl radicals can be substituted by one or morenon-aromatic substituents R³,

m and n are each an integer 0, 1, 2 or 3, preferably 0 or 1,

X and Y are identical or different and are halogen, preferably Cl, Br orI, B(OR⁷)₂ or SnR⁷R⁸R⁹, and

R⁷, R⁸ and R⁹ are identical or different and are H or C₁-C₆-alkyl, wheretwo radicals can also form a common ring and these radicals can also bebranched or unbranched.

Examples of monomers are shown in Scheme 2 below:

The suitable 9-Aryl¹-9-Aryl²-fluorene monomers can be synthesized, forexample, as described in Scheme 3 below:

In the above formulae, Ar¹ is a radical R¹ and Ar² is a radical R².

The radical R is as defined above (Schemes 1 and 2). According to this,simple fluorenone derivatives are halogenated. For m and n=0, thiscorresponds to the halogenation of fluorenone. 2,7-Dibromofluorenone,for example, is commercially available (for example Aldrich). It ispossible subsequently to introduce a first aryl group by the standardGrignard reaction. This can be carried out, for example, as described inOrganikum (15th Edition, 1977, page 623).

A phenol derivative can subsequently be added on with acid catalysis.This can be carried out analogously to the descriptions in WO 92/07812.The resultant compound can be etherified. This can be carried out, forexample, by the Williamson method (cf. Organikum, 15th Edition, 1977,page 253).

The resultant compounds (bishalofluorene derivatives) can be used asmonomers as they are. Further reaction (metallation with subsequentreaction either with borates or trialkyltin halide) enables furthermonomers to be obtained: fluorenebisboronic acid derivatives, fluorenebisstannates or, with corresponding stoichiometry, alsomonohalofluorenemonoboronic acid derivatives or monohalofluorenemonostannates. This last-mentioned reaction can be carried out bystandard methods, as described, for example, in WO 98/27136.

Another method is shown in the following scheme:

The radicals here are defined as Aryl¹ =Ar¹ =R¹ and Aryl²=Ar²=R².

Starting from bishalogenated fluorenone derivatives (see above), firstly4,4′-dihalobiphenyl-2-carboxylate derivatives can be obtained asintermediate by basic ring-opening with subsequent esterification. Thesecompounds can then be converted into the desired fluorene monomers byreaction with two different aryl-Grignard reagents, where interimhydrolysis in order to isolate the corresponding ketone as intermediatehas proven helpful, followed by acidic cyclization.

As already mentioned above, a further reaction is also possible here togive the corresponding fluorenebisboronic acid derivatives, fluorenebisstannates or monohalofluorenemonoboronic acid derivatives ormonohalofluorene monostannates.

This has shown that monomers which are preferably converted intopolymers according to invention by the polymerization methods describedabove are readily accessible.

The polymers obtained in this way are very particularly preferablysuitable as organic semiconductors and in particular aselectroluminescent materials.

For the purposes of the present invention, the term “electroluminescentmaterials” is taken to mean materials which can be used as the activelayer in an electroluminescent device. “Active layer” means that thelayer is capable of emitting light on application of an electric field(light-emitting layer) and/or that it improves the injection and/ortransport of positive and/or negative charges (charge injection orcharge transport layer).

The invention therefore also relates to the use of a polymer accordingto the invention as electroluminescent material and as organicsemiconductor.

In order to be used as electroluminescent materials, the polymersaccording to invention are generally applied to a substrate in the formof a film by known methods which are customary to the person skilled inthe art, such as dipping or spin coating.

The invention thus likewise relates to an electroluminescent devicehaving one or more active layers, where at least one of these activelayers comprises one or more polymers according to the invention. Theactive layer can be, for example, a light-emitting layer and/ortransport layer and/or a charge injection layer.

The general construction of such electroluminescent devices isdescribed, for example, in U.S. Pat. No. 4,539,507 and U.S. Pat. No.5,151,629. Electroluminescent devices containing polymers are described,for example, in WO 90/13148 and EP-A-0 443 861.

They usually contain an electroluminescent layer between a cathode andan anode, at least one of the electrodes being transparent. In addition,one or more electron injection and/or electron transport layers can beinstalled between the electroluminescent layer and the cathode and/orone or more hole injection and/or hole transport layers can be installedbetween the electroluminescent layer and the anode. The cathode canpreferably be a metal or metallic alloy, for example Ca, Sr, Ba, Mg, Al,In or Mg/Ag. The anode can be a metal, for example Au, or anothersubstance which conducts in a metallic manner, such as an oxide, forexample ITO (indium oxide/tin oxide), on a transparent substrate, forexample of glass or transparent polymer.

In operation, the cathode is set to a negative potential compared withthe anode. Electrons are injected by the cathode into the electroninjection layer/electron transport layer or directly into thelight-emitting layer. At the same time, holes are injected by the anodeinto the hole injection layer/hole transport layer or directly into thelight-emitting layer.

The injected charge carriers move toward one another through the activelayers under the influence of the applied voltage. This results inelectron/hole pairs at the interface between the charge transport layerand the light-emitting layer or within the light-emitting layer; thesepairs recombine with emission of light. The color of the emitted lightcan be varied through the materials used as light-emitting layer.

Electroluminescent devices are used, for example, as self-illuminatingdisplay elements, such as control lamps, alphanumeric displays,monochromic or multichromic matrix displays, signs, electro-opticalstorage media and in opto-electronic couplers.

Various documents are cited in the present application, in order, forexample, to illustrate the technical background to the invention. Allthese documents are expressly incorporated herein by way of reference.

The invention is described in greater detail by the examples, withoutthis being intended to represent a limitation.

A) Synthesis of the Monomers

1. Preparation of the monomers according to the invention:

EXAMPLE M1 Preparation of2,7-Dibromo-9-(2,5-dimethylphenyl)-9-[4-(3,7-dimethyloctyloxy)phenyl]fluorene

i) 2,7-Dibromo-9-(2,5-dimethylphenyl)fluoren-9-ol:

The Grignard reagent made from 102 g of bromo-p-xylene, prepared in thecustomary manner in THF, was added dropwise to a suspension of2,7-dibromofluorenone (169 g) in 500 ml of THF at 5-15° C. The batch wassubsequently refluxed for two hours. For hydrolysis, about 1200 ml ofice-water and 30 ml of concentrated sulfuric acid were added. The phaseswere separated, the aqueous phase was back-shaken a number of times withethyl acetate, and the combined organic phases were back-shaken againwith water. After drying over Na₂SO₄, the solvent was removed, and theresultant crude product was recrystallized from ethanol.

Yield: 163 g (73%). ¹H-NMR (d₆-DMSO): [ppm] δ=8.05 (s (br), 1H, OH),7.85 (d, 2H, H-4, J=8 Hz), 7.60 (dd, 2H, H-3, J₁=1 Hz, J₂=8 Hz), 7.15(d, 2H, H-1, J=2 Hz), 7.02 (dd (br), 1H, H-4′, J₁=2 Hz, J₂=8 Hz), 6.85(d, 1H, H-3′, J=7.5 Hz), 6.48 (s (br), 1H, H-6′), 2.38 (s, 3H, Me), 1.2(s (br), 3H, Me).

ii) 2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-hydroxyphenyl)fluorene

9.5 g of phenol were mixed with 22.2 g of2,7-dibromo-9-(2,5-dimethylphenyl)fluoren-9-ol, 25 ml of toluene and 0.1ml of mercapto-propionic acid. 5 ml of concentrated sulfuric acid weresubsequently added dropwise. The batch was then stirred at 60° C. forabout 2 hours, and finally 100 ml of MeOH and 100 ml of water wereadded. The solid was filtered off with suction and further purified bystirring with ethanol.

Yield: 16 g (61%). ¹H-NMR (d₆-DMSO): [ppm] δ=9.4 (s (br), 1H, OH), 7.92(d, 2H, H-4, J=8 Hz), 7.60 (dd, 2H, H-3, J₁=1 Hz, J₂=8 Hz), 7.45 (d, 2H,H-1, J=2 Hz), 6.98 (m, 4H, H-2″, H-3′, H-4′), 6.87 (s (br), 1H, H-6′),6.67 (part of an M′BB′, 2H, H-3″), 2.17 (s, 3H, Me), 1.38 (s(br), 3H,Me).

iii)2,7-Dibromo-9-(2,5-dimethylphenyl)-9-[4-(3,7-dimethyloctyloxy)phenyl]-fluorene

52 g of 2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-hydroxyphenyl)fluorenewere refluxed with 18 g of 3,7-dimethyloctyl chloride, 80 ml of ethanol,7 g of KOH and 1 g of NaI for 5 days. According to TLC, the reaction wascomplete after this time. The solvent was stripped off, ethyl acetatewas added, and the precipitate was filtered off with suction and rinseda number of times with ethyl acetate. The organic phase was dried, andthe solvent was stripped off.

The product was purified by bidistillation in a short-path evaporator(10⁻³ mbar; 1st distillation for drying: 80° C.; 2nd distillation: 250°C.).

Yield: 48 g (73%). ¹H-NMR (CDCl₃): [ppm] δ=7.83 (d, 2H, H-4, J=8 Hz),7.55 (dd, 2H, H-3, J₁=1 Hz, J₂=8 Hz), 7.38 (d, 2H, H-1, J=2 Hz), 7.02(m, 4H, H-2″, H-3′, H-4′), 6.92 (s (br), 1H, H-6′), 6.77 (part of anM′BB′, 2H, H-3″), 3.90 (m, 2H; OCH₂), 2.17 (s, 3H, Me), 1.80 (m, 1H),1.65 (m, 3H), 1.38 (s (br), 3H, Me), 1.30 (m, 3H); 1.16 (m, 3H), 0.93(d, 3H, CH₃, J=6.6 Hz), 0.86 (d, 6H; 2×CH₃, J=6.7 Hz).

EXAMPLE M2 Preparation of Bisethylene Glycol9-(4-(3,7-Dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronate

Under a nitrogen atmosphere, (86.0 g, 130 mmol) of2,7-dibromo-9-(4-(3,7-dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorenewere dissolved in 300 ml of distilled THF, and the solution was addeddropwise to 7.29 g (300 mmol) of magnesium with gentle warming. Themixture was subsequently refluxed for 3 hours. The mixture was thendiluted with 100 ml of distilled THF and cooled to room temperature.34.3 g (330 mmol) of trimethyl borate were dissolved in 500 ml ofdistilled THF in a 2 l flask and cooled to −78° C. The Grignard solutionwas slowly added dropwise at this temperature at such a rate that thetemperature did not exceed −70° C. (2 hours). The mixture was slowlywarmed to room temperature overnight with stirring.

500 ml of ice-water and 32.5 ml of concentrated sulfuric acid were addedto the jelly-like material (greenish), the mixture was stirred for 60minutes, and the organic phase was separated off. The water phase wasextracted once with 100 ml of ethyl acetate. The organic phases werecombined and washed with saturated NaCl, dried over MgSO₄ and evaporatedin a rotary evaporator, giving 88.1 g of crude product. This wassuspended twice in 400 ml of n-hexane, stirred at RT for 60 minutes,filtered off with suction and dried at RT in a vacuum drying cabinet(yield 67.5 g). The boronic acid was dissolved in 450 ml ofdichloromethane, and 13 g of ethylene glycol and 0.8 ml of sulfuric acidwere added. The mixture was refluxed for 5 hours on a water separator,cooled, washed with 100 ml of water (these phases were extracted with150 ml of dichloromethane) and dried using MgSO₄. The product wasevaporated in a rotary evaporator, and the residue was recrystallizedtwice from a mixture of 600 ml of n-hexane and 70 ml of ethyl acetate,giving 24.5 g (32%) of bisethylene glycol9-(4-(3,7-dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronateas colorless crystals with a purity (NMR) of greater than 99%.

¹H-NMR (CDCl₃): [ppm] δ=7.95-7.75 (m, 6H, fluorene); 7.17 (d, 2H, J=8Hz, H-2′); 6.95 (br. s, 1H, H-2″); 6.90 (d, 1H, J=8 Hz, H-4″); 6.84 (d,1H, J=8 Hz, H-5″); 4.34, (s, 8H, boronate); 3.95-3.85 (m, 2H, OCH₂);2.20 (s, 3H, CH₃); 1.80-1.45 (m, 4H); 1.35 (3H, CH₃); 1.32-1.10 (m, 6H,alkyl); 0.90 and 0.85 (2d, 9H, 3×CH₃).

2. Preparation of Further Comonomers:

EXAMPLE CM1 Preparation of 2,7-Dibromo-9,9-bis(2-ethylhexyl)fluorene

The preparation was carried out analogously to Example 1 of WO 97/05184.The product (84% yield) was isolated as a high-viscosity, pale yellowoil by bidistillation in a short-path evaporator [10⁻³ mbar; 1stdistillation (for removing excess ethylhexyl bromide and residual DMSO)100° C.; 2nd distillation: 155° C.].

¹H-NMR (CDCl₃): [ppm] δ=7.54-7.43 (m, 6H, H-aryl); 1.93 (d with Fs., 4H,J=4.0 Hz); 1.0-0.65 (m, 22H, H-alkyl); 0.58-0.45 (m, 8H, H-alkyl).

EXAMPLE CM2 Preparation of Bisglycol9,9-bis(2-Ethylhexyl)fluorene-2,7-bisboronate

Magnesium (6.32 g, 0.26 mol) was initially introduced in 10 ml of THF, alittle iodine was added, and a few drops of2,7-dibromo-9,9-bis(2-ethylhexyl)fluorene were added. The initiation ofthe reaction was evident from considerable exothermicity. The remainderof the bisbromide (a total of 68.56 g, 0.125 mol) and 300 ml of THF weresubsequently added dropwise in parallel. When the addition was complete,the mixture was refluxed for about 5 hours. Small amounts of Mg turningswere still evident. In parallel, trimethyl borate (28.6 g, 0.27 mol) inTHF (200 ml) was initially introduced and cooled to −70° C. At thistemperature, the Grignard solution was slowly added dropwise. Themixture was subsequently slowly warmed to room temperature overnightwith stirring.

The reaction solution was added to 300 ml of ice-water and 10 ml ofconcentrated sulfuric acid, and the organic phase was separated off. Theorganic phase was then washed (neutral) once with water. After dryingover Na₂SO₄, the mixture was evaporated in a rotary evaporator. Thecrude product was stirred with hexane (500 ml). This gave the crudebisboronic acid (containing variable amounts of various anhydrides).

This was esterified directly by refluxing (12 hours) in toluene withethylene glycol and sulfuric acid on a water separator.

Yield over the two steps: 70-85%. Purity (NMR)>98.5% ¹H-NMR (CDCl₃):(NMR signals greatly broadened or doubled due to diastereomerism) δ=7.86(m, 2H, H-1), 7.79 (m, 2H, H-3), 7.73 (d, 2H, H-4, J=8 Hz), 4.38 (s(br), 8H, O—CH₂), 2.02 (m, 4H, C—CH₂—), 0.75 (m (br), 22H, H-alkyl),0.47 (m (br), 8H, H-alkyl).

EXAMPLE CM3 Preparation of 4,4′-Dibromotriphenylamine

The preparation was carried out analogously to K. Haga et al, Bull.Chem. Soc. Jpn., 1986, 59, 803-7: 3.10 g (10.4 mmol) ofbis(4-bromophenyl)amine (J. Berthelot et al, Can. J. Chem., 1989, 67,2061), 1.28 g of cyclohexane-1,4-dione (11.4 mmol) and 2.17g (11.4 mmol)of p-toluenesulfonic acid hydrate were heated in 50 ml of toluene on awater separator. After a reaction time of 12 hours, the solvent wasremoved and the product was purified by column chromatography(hexane/ethyl acetate 4:1). 3.82 g (9.46 mmol, 91%) of4,4′-dibromotriphenylamine were obtained as a viscous oil.

¹H-NMR (CDCl₃): [ppm] δ=7.01-6.95 (m, 5H), 6.88, 6.74 (AA′BB′, 4+4H).

B) Synthesis of the Polymers: EXAMPLE P1 Copolymerization of Bisglycol9,9-bis(2-Ethylhexyl)fluorene-2,7-bisboronate and2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneby the Suzuki Reaction (Polymer P1)

13.21 g (20 mmol) of2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneand 11.61 g of K₂CO₃ (84 mmol) were dissolved in 25 ml of toluene and 25ml of water and aerated with N₂. 7.743 g (14.6 mmol) of bisglycol9,9-bis(2-ethylhexyl)fluorene-2,7-bisboronate and 200 mg of Pd(PPh₃)₄(0.17 mmol) were added under a protective gas. The yellow-brownish,cloudy suspension was stirred vigorously at an internal temperature of87° C. under an N₂ blanket. On each of the following three days, 1.11 g(2.1 mmol) of the diboronate were added. After 3 days, a further 25 mlof toluene were added to the very viscous mixture. After a total of 4days, the mixture was worked up.

The reaction solution was diluted with 150 ml of toluene, and thesolution was stirred for 3 hours with 200 ml of 2% aqueous NaCN. Duringthis operation, the mixture became almost completely colorless. Thebatch was transferred into a separating funnel under a protective gas.The organic phase with washed with H₂O and precipitated by addition to500 ml of ethanol.

The polymer was dissolved in 635 ml of THF at 40° C. for 1 hour andprecipitated using 640 ml of MeOH, washed and dried under reducedpressure (10.13 g). The product was re-precipitated again from 405 ml ofTHF/400 ml of methanol, filtered off with suction and dried to constantweight, giving 7.55 g (42%) of polymer P1 as a pale yellow solid.

¹H-NMR (CDCl₃): [ppm] δ=8.1-6.3 (m, 19H, H-fluorene, H-phenyl); 4.0 (m,2H, OCH₂); 2.3-0.4 (m, 59H, alkyl+alkoxy-H). GPC: THF+0.25% oxalic acid;column set SDV500, SDV 1000, SDV10000 (PPS), 35° C., UV detection 254nm: M_(w)=156000 g/mol, M_(n)=88000 g/mol. UV-VIS (film): λ_(max)=372nm; PL (film): λ_(max)=413 nm, 433 nm.

EXAMPLE P2 Copolymerization of Bisethylene Glycol9-(4-(3,7-Dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronate,2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneand 1 mol-% of 4,4′-Dibromotriphenylamine by the Suzuki Reaction(Polymer P2)

6.4733 g (9.8 mmol) of2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluorene,6.4246 g (10.00 mmol) of bisethylene glycol9-(4-(3,7-dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronate,80.6 mg (0.2 mmol) of 4,4′-dibromotriphenylamine, 9.67 g (42 mmol) ofK₃PO₄ hydrate, 30 ml of toluene, 15 ml of water and 0.25 ml of ethanolwere degassed for 30 minutes by passing N₂ through the mixture. 175 mg(0.15 mmol) of Pd(PPh₃)₄ were subsequently added under a protective gas.The suspension was stirred vigorously at an internal temperature of 87°C. (gentle reflux) under an N₂ blanket. After 4 days, a further 0.30 gof bisethylene glycol9-(4-(3,7-dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronatewere added. After the mixture had been heated for a further 6 hours, 0.3ml of bromobenzene was added, and the mixture was refluxed for a further3 hours.

The reaction solution was diluted with 200 ml of toluene, and thesolution was stirred for 3 hours with 200 ml of 2% aqueous NaCN. Duringthis operation, the mixture became almost completely colorless. Theorganic phase was washed with H₂O and precipitated by addition to 800 mlof ethanol.

The polymer was dissolved in 200 ml of THF at 40° C. for 1 hour andprecipitated using 250 ml of MeOH, washed and dried under reducedpressure. The product was re-precipitated again from 200 ml of THF/250ml of methanol, filtered off with suction and dried to constant weight,giving 9.3 g (18.5 mmol, 93%) of polymer P2 as a pale yellow solid.

¹H-NMR (CDCl₃): [ppm] δ=7.8 (m, 2H, fluorene); 7.55 (br. s; 4H,fluorene) 7.15 (br. s, 2H phenyl); 7.0-6.9 (m, 3H, 2,5-dimethylphenyl);6.7 (br. s, 2H, phenyl), 3.95 (br. s, 2H, OCH₂), 2.1 (s, 3H, CH₃); 1.7(m, 1H, alkyl); 1.6 (s, 3H, CH₃); 1.5-0.8 (m, 18H, alkyl). GPC:THF+0.25% oxalic acid; column set SDV500, SDV 1000, SDV10000 (PPS), 35°C., UV detection 254 nm: M_(w)=43000 g/mol, M_(n)=23000 g/mol.Electroluminescence: λ_(max)=448 nm; result at max. eff.: 0.44 cd/A at6.7 V/46.9 mA/cm²/202 cd/m². 100 cd/m² was achieved at a voltage of 6.3V and a current density of 24.4 mA/cm².

EXAMPLE P3 Polymerization of Bisethylene Glycol9-(4-(3,7-Dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronateand2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneby the Suzuki Reaction (Polymer P3)

Analogously to Example P2, 6.6054 g (10.00 mmol) of2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluorene,6.4246 g (10.00 mmol) of bisethylene glycol9-(4-(3,7-dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronateand 9.67 g (42 mmol) of K₃PO₄ hydrate were polymerized in 30 ml oftoluene, 15 ml of water and 0.25 ml of ethanol with the aid of 175 mg(0.15 mmol) of Pd(PPh₃)₄. End-capping, analogous work-up andpurification gave 9.1 g (18.2 mmol, 91%) of polymer P3 as a pale yellowsolid.

¹H-NMR (CDCl₃): [ppm] δ≦7.8 (m, 2H, fluorene); 7.55 (br. s; 4H,fluorene) 7.15 (br. s, 2H phenyl); 7.0-6.9 (m, 3H, 2,5-dimethylphenyl);6.7 (br. s, 2H, phenyl), 3.95 (br. s, 2H, OCH₂), 2.1 (s, 3H, CH₃); 1.7(m, 1H, alkyl); 1.6 (s, 3H, CH₃); 1.5-0.8 (m, 18H, alkyl). GPC:THF+0.25% oxalic acid; column set SDV500, SDV 1000, SDV10000 (PPS), 35°C., UV detection 254 nm: M_(w)=47000 g/mol, M_(n)=27000 g/mol.Electroluminescence: λ_(max)=447 nm; result at max. eff.: 0.18 cd/A at7.2 V/57.3 mA/cm². 100 cd/m² was achieved at a voltage of 7.3 V and acurrent density of 62.1 mA/cm².

EXAMPLE P4 Polymerization of Bisethylene Glycol9-(4-(3,7-Dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronate,2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneand 3% of 4,4′-Dibromotriphenylamine by the Suzuki Reaction (Polymer P4)

Analogously to Example P2, 9.328 g (14.10 mmol) of2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluorene,7.955 g (15.00 mmol) of bisethylene glycol9,9-bis(2-ethylhexyl)fluorene-2,7-bisboronate, 362.8 mg (0.9 mmol) of4,4′-dibromotriphenylamine and 8.71 g (62 mmol) of K₂CO₃ werepolymerized in 30 ml of toluene, 15 ml of water and 0.3 ml of ethanolwith the aid of 260 mg (0.225 mmol) of Pd(PPh₃)₄. End-capping, analogouswork-up and purification gave 11.1 g (24.9 mmol, 83%) of polymer P4 as apale yellow solid.

¹H-NMR (CDCl₃): [ppm] δ=7.85 (m, 1H fluorene); 7.75-7.45 (br. m; 4H,fluorene); 7.28 (m, 1H, fluorene); 7.1 (br. s, 1H phenyl); 7.0-6.9 (m,1.5H, 2,5-dimethylphenyl); 6.75 (br. s, 2H, phenyl), 3.95 (br. s, 1H,OCH₂), 2.23 (s, 2H, CH₂); 2.1-0.5 (m, 27.5H, alkyl). GPC: THF+0.25%oxalic acid; column set SDV500, SDV 1000, SDV10000 (PPS), 35° C., UVdetection 254 nm: M_(w)=47000 g/mol, M_(n)=27000 g/mol.Electroluminescence: λ_(max)=446 nm; PL: λ_(max)=425, 452 nm; result atmax. eff.: 0.36 cd/A at 7.5 V174.3 mA/cm²/271 cd/m². 100 cd/m² wasachieved at a voltage of 6.6 V and a current density of 30.6 mA/cm².

EXAMPLE P5 Polymerization of Bisethylene Glycol9-(4-(3,7-Dimethyloctyloxy)phenyl)-9-(2,5-dimethylphenyl)fluorene-2,7-bisboronate,2,7-Dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluoreneand 1% of 4,4′-Dibromotriphenylamine by the Suzuki Reaction (Polymer P5)

Analogously to Example P2, 12.966 g (19.6 mmol) of2,7-dibromo-9-(2,5-dimethylphenyl)-9-(4-(3,7-dimethyloctyloxy)phenyl)fluorene,10.607 g (20.00 mmol) of bisethylene glycol9,9-bis(2-ethylhexyl)fluorene-2,7-bisboronate, 161 mg (0.4 mmol) of4,4′-dibromotriphenylamine and 11.61 g (84 mmol) of K₂CO₃ werepolymerized in 40 ml of toluene, 20 ml of water and 0.5 ml of ethanolwith the aid of 350 mg (0.3 mmol) of Pd(PPh₃)₄. End-capping, analogouswork-up and purification gave 12.2 g (27.4 mmol, 68%) of polymer P5 as apale yellow solid.

¹H-NMR (CDCl₃): [ppm] δ=7.85 (m, 1H fluorene); 7.75-7.45 (br. m; 4H,fluorene); 7.28 (m, 1H, fluorene); 7.1 (br. s, 1H phenyl); 7.0-6.9 (m,1.5H, 2,5-dimethylphenyl); 6.75 (br. s, 2H, phenyl), 3.95 (br. s, 1H,OCH₂), 2.23 (s, 2H, CH₂); 2.1-0.5 (m, 27.5H, alkyl). GPC: THF+0.25%oxalic acid; column set SDV500, SDV 1000, SDV10000 (PPS), 35° C., UVdetection 254 nm: M_(w)=53000 g/mol, M_(n)=31000 g/mol.Electroluminescence: λ_(max)=446 nm; PL: λ_(max)=425, 452 nm; result atmax. eff.: 0.14 cd/A at 5.7V/77.0 mA/cm²/110 cd/m². 100 cd/m² wasachieved at a voltage of 5.7 V and a current density of 83.0 mA/cm².

COMPARATIVE EXAMPLES EXAMPLE C1 Suzuki Polymerization of2,7-Dibromo-9,9-bis(2-ethylhexyl)fluorene and Bisglycol9,9-bis(2-Ethylhexyl)fluorene-2,7-bisboronate (Polymer C1), Preparationof Poly-2,7-[9,9-bis(2-ethylhexyl)fluorene]

8.227 g (15.00 mmol) of 2,7-dibromo-9,9-bis(2-ethylhexyl)fluorene, 7.956g (15.00 mmol) of diethylene glycol9,9-bis(2-ethylhexyl)fluorene-2,7-bisboronate, 8.71 g (63 mmol) ofK₂CO₃, 25 ml of toluene and 15 ml of water were degassed for 30 min bypassing N₂ through the mixture. 230 mg (0.2 mmol) of Pd(PPh₃)₄ weresubsequently added under a protective gas. The suspension was stirredvigorously at an internal temperature of 87° C. (gentle reflux) under anN₂ blanket. After 2 days, a further 20 ml of toluene were added, andafter a further 2 days, a further 0.20 g of diethylene glycol9,9-bis(2-ethylhexyl)fluorene-2,7-bisboronate were added. After afurther 6 hours, 0.5 ml of 4-bromofluorobenzene was added, and themixture was refluxed for a further 3 hours.

Work-up was carried out as described under Example P1, giving 3.85 g(9.9 mmol, 33%) of polymer C1 a pale beige solid.

¹H-NMR (CDCl₃): [ppm] δ=7.9-7.3 (m, 6H, H-aromatic); 2.15 (br. s, 4H,C(9)—CH₂); 1.1-0.4 (m, 30H, H-alkyl). GPC: THF+0.25% oxalic acid; columnset SDV500, SDV 1000, SDV10000 (PPS), 35° C., UV detection 254 nm:M_(w)=70000 g/mol, M_(n)=34000 g/mol. UV-VIS (film): λ_(max)=376 nm; PL(film): λ_(max)=420 nm, 444 nm.

C) Measurements

Whereas polymer C1 gave green-yellow emission (maximum at about 540 nm)in a typical EL device, polymer P1 according to the invention exhibitedstrong blue luminescence (wavelength at about 460 nm). This colorremained constant even during an extended observation time.

What is claimed is:
 1. A conjugated polymer which contains structuralunits of the formula

in which R¹ and R² are two different substituents selected from thegroup consisting of C₂-C₄₀-heteroaryl and C₅-C₄₀-aryl, wherein said aryland said heteroaryl independently of one another are optionallysubstituted by one or more substituents R³, R³ and R⁴ are identical ordifferent and are C₁-C₂₂-alkyl, C₂-C₂₀-heteroaryl, C₅-C₂₀-aryl, F, Cl,CN, SO₃R⁵ or NR⁵R⁶, wherein said alkyl is branched, unbranched oralternatively is cycloalkyl radical, and individual, non-adjacent CH₂group(s) of the alkyl radical are optionally replaced by O, S, C═O, COO,N—R⁵ or a simple aryl, wherein the above mentioned said aryls areoptionally substituted by one or more non-aromatic substituents R³, R⁵and R⁶ are identical or different and are H, C₁-C₂₂-alkyl,C₂-C₂₀-heteroaryl or C₅-C₂₀-aryl, wherein said alkyl is branched orunbranched or alternatively is a cycloalkyl radical, and individual,non-adjacent CH₂ group(s) of the alkyl radical is optionally replaced byO, S, C═O, COO, N—R⁵ or a simple aryl radical, wherein the abovementioned said aryls are optionally substituted by one or morenon-aromatic substituents R³ and m and n are each identical or differentand are an integer 0, 1, 2 or
 3. 2. The polymer as claimed in claim 1,wherein the polymer contains at least 10 mol % of structural units ofthe formula (I) incorporated randomly, alternately, periodically or inblocks.
 3. The polymer as claimed in claim 1, which comprises from 10 to10,000 recurring structural units of the formula (I).
 4. The polymer asclaimed in claim 1, wherein m and n are zero.
 5. An organicsemiconductor which comprises the polymer as claimed in claim
 1. 6. Anelectroluminescent device containing the polymer as claimed in claim 1.7. A compound of the formula (A)

in which R¹ and R² are two different substituents selected from thegroup consisting of C₂-C₄₀-heteroaryl and C₅-C₄₀-aryl, wherein said aryland said heteroaryl independently of one another are optionallysubstituted by one or more substituents R³, R³ and R⁴ are identical ordifferent and are C₁-C₂₂-alkyl, C₂-C₂₀-heteroaryl, C₅-C₂₀-aryl, F, Cl,CN, SO₃R⁵ or NR⁵R⁶, wherein said alkyl is branched, unbranched oralternatively is a cycloalkyl, and individual, non-adjacent CH₂ group(s)of the alkyl radical is optionally replaced by O, S, C═O, COO, N—R⁵ or asimple aryl radical, wherein said above mentioned aryls are optionallysubstituted by one or more non-aromatic substituents R³, R⁵ and R⁶ areidentical or different and are H, C₁-C₂₂-alkyl, C₂-C₂₀-heteroaryl orC₅-C₂₀-aryl, wherein said alkyl is branched or unbranched oralternatively is a cycloalkyl, and individual, non-adjacent CH₂ group(s)of the alkyl radical is optionally replaced by O, S, C═O, COO, N—R⁵ or asimple aryl radical, wherein said above mentioned aryls are optionallysubstituted by one or more non-aromatic substituents R³, m and n areidentical or different and are each an integer 0, 1, 2 or 3 X and Y areidentical or different and are halogen, B(OR⁷)₂ or SnR⁷R⁸R⁹, and R⁷, R⁸and R⁹ are identical or different and are H or C₁-C₆-alkyl, wherein tworadicals optionally form a common ring and these radicals are optionallybranched or unbranched.
 8. The polymer as claimed in claim 1 wherein R¹and R² are two different substituents wherein each is a C₆-arylsubstituted by one or more substituents R³ wherein R³ is alkyl and saidindividual nonadjacent CH₂ group(s) of the alkyl radical are optionallyreplaced by O.
 9. The compound as claimed in claim 7 wherein R¹ and R²are two different substituents wherein each is a C₆-aryl substituted byone or more substituents R³ wherein R³ is alkyl and said individualnonadjacent CH₂ group(s) of the alkyl radical are optionally replaced byO.
 10. The compound as claimed in claim 7 wherein m and n are 0.